[Establishment of a pharmacogenomic testing system for the realization of individual pharmacotherapy]

The metabolism of and sensitivity to drugs differ from individual to individual, and one base polymorphism of drug-metabolizing enzymes is known to play an important role in this difference between individuals. The genotyping of drug-metabolizing enzymes prior to drug administration would help to predict individual reactivity to drugs and possible adverse reactions that may occur, which is essential to realize tailor-made therapy for individual patients. In July 2005, the Pharmacogenomics Working Group, composed of members of the Clinical Genomic Medicine Unit, Pharmaceutical Department, Medical Informatics Department, Clinical Laboratory, Gastroenterology, Cardiovascular Medicine, and Department of Neurology, was established in our university hospital in an attempt to introduce such pharmacogenomic testing. The project was approved by the Institutional Research Ethics Committee of the Faculty of Medicine, the University of Tokyo, and, in August 2006, testing for CYP2C19*2 and CYP2C19*3, enzymes involved in the metabolism of proton pump inhibitors, was started. Furthermore, in August 2007, testing for CYP2C9*3, the enzyme involved in the metabolism of Warfarin, and vitamin K epoxidereductase1 (VKORC1) 6484 C>T was started. In the CYP2C19 genotyping, the high incidence of poor metabolizers has been demonstrated; it was speculated that the test could confirm the adverse effects of the drug, i.e., after administration of the drug to patients. Moreover, testing for CYP2C9*3 and VKORC1 6484 C>T was shown to be useful for the safe administration of warfarin. The pharmacogenomic testing system was successfully established in our university hospital, and the Pharmacogenomics Working Group is still active, playing an important role in this project.